Plasma surgery is a form of high-frequency surgery in which a high-frequency electrical alternating current (HF current) is passed through electrically ionized and consequently electrically conductive noble gas (plasma), in particular argon (argon plasma) or helium (helium plasma), and applied to the tissue to be treated in order to produce surgically relevant thermal effects in this target tissue. The noble gas that has most often been used for this purpose is argon, and the best-known thermal effect in the tissue is coagulation, for which reasons this procedure is also known as “argon-plasma coagulation (APC)”. In principle other gases or gas mixtures could be used instead of a noble gas for plasma surgery. For example, for over 50 years air has been used as the gas, in which case the procedure is known as fulguration or spray-coagulation. However, noble gases offer the advantage that they do not cause any chemical effects, i.e. they have a chemically neutral behavior. This advantage can be utilized in particular for the endoscopic application of plasma surgery, where the view would be obstructed by unavoidable smoke formation if air were employed, and the burning or vaporization of biological tissue inevitably associated with the use of air could lead to severe complications, such as the perforation of organ walls.
For both open incisions and minimally invasive operations plasma surgery has been used for more than 20 years primarily to stop bleeding by thermal means, namely by means of the thermal coagulation of the biological tissue. In this process either the air already present serves as the required gas, as in the case of fulguration or spray coagulation, or a noble gas is used, in which case the procedure is called argon-plasma coagulation because the gas most often used is argon.
Since catheter-like, flexible instruments have been developed for APC, which can be inserted through a working or instrumentation channel of flexible endoscopes (G. Farin et al.: Technology of Argon Plasma Coagulation with Particular Regard to Endoscopic Applications; Endoscopic Surgery and Allied Technologies, No. 1, Vol. 2, February 1994, 71-77), APC can also be used in flexible endoscopy. It soon became clear that there is a broad spectrum of indications for the APC procedure in this area. Apart from thermal hemostasis, APC is used in flexible endoscopy for tasks such as the thermal destruction or thermal devitalization of pathological tissue (Grund K. E., Storek D., Farin G.: Endoscopic Argon Plasma Coagulation (APC)—First Clinical Experiences in Flexible Endoscopy. Endoscopic Surgery and Allied Technologies, No. 1, Vol. 2, February 1994, 42-46). Although the term argon-plasma coagulation (APC) is now too narrow in view of the recent indications for this procedure in flexible endoscopy, and “plasma surgery” would be more suitable, here “argon-plasma: coagulation (APC)” will continue to be used for this procedure, but without limiting the procedure to the noble gas argon or to coagulation as the thermal effect.
The apparatus available since 1992 for application of APC in flexible endoscopy is described in the German patent DE 41 39 029.
A known problem in employing thermal methods within the gastrointestinal tract, as well as in the tracheobronchial system and the throat region, is the risk that combustible or even explosive substances will be unintentionally ignited. The gastrointestinal tract may contain combustible endogenous gases that can be ignited by the relatively high temperature of the plasma. In the tracheobronchial system the respired gas may have a high oxygen concentration or the patient may even be breathing pure oxygen, so that ignition of combustible substances by the hot plasma can result in an intense fire. Several cases of damage caused in this way are known, both with and without a lethal outcome. Although noble gases cannot cause a fire, damage by fire and/or explosions has been known to occur even when APC is being used.